As a conventional inkjet recording method, a piezo method for jetting an ink droplet by changing a shape of an ink passage according to vibration of a piezoelectric element, a thermal method for making a heat generator provided in an ink passage heat to generate air bubbles and jetting an ink droplet according to a pressure change by the air bubbles in the ink passage, and an electrostatic sucking method for charging ink in an ink passage to jet an ink droplet by a electrostatic sucking power of the ink are known.
An ink jet printer described in JP-Tokukaihei-11-277747 is cited as a conventional electrostatic sucking type ink jet printer. The ink jet printer comprises a plurality of convex ink guides for jetting ink from an edge portion thereof, a counter electrode which is arranged to face the edge of each ink guide and is grounded, and a jetting electrode for applying a jetting voltage to ink for each ink guide. Two kinds of the convex ink guides with different widths of slits to guide ink are prepared to have a feature to be able to jet an ink droplet with two kinds of sizes by appropriately using them.
The conventional ink jet printer jets an ink droplet by applying a pulse voltage to the jetting electrode, and guides the ink droplet to the counter electrode side by electric field formed between the jetting electrode and the counter electrode.
However, the above-mentioned inkjet recording method has the following problems.
(1) Limit and Stability of a Minute Liquid Droplet Formation
Since a nozzle diameter is large, a shape of a droplet jetted from a nozzle is not stabilized, and there is a limit of making a droplet minute.
(2) High Applying Voltage
For jetting a minute droplet, miniaturization of a jet opening of the nozzle is an important factor. In a principle of the conventional electrostatic sucking method, since the nozzle diameter is large, electric field intensity of a nozzle edge portion is weak, and therefore, in order to obtain necessary electric field intensity for jetting a droplet, it is necessary to apply a high jetting voltage (for example, extremely high voltage near 2000 [V]). Accordingly, in order to apply a high voltage, a driving control of a voltage becomes expensive.
Moreover, in the patent document 1 as the conventional example, ink jetting is performed only by applying a pulse voltage to the ink, so a high voltage needs to be applied to the electrode to which the pulse voltage is applied. Thus, there is a disadvantage to accelerate the above (2) and (3) problems.
Thereupon, to provide a liquid jetting apparatus capable of jetting a minute droplet is a first object. At the same time, to provide a liquid jetting apparatus capable of jetting a stable droplet is a second object. Further, to provide a liquid jetting apparatus which can reduce an applying voltage and is cheap is a third object.